Flyzone's
new release is bound to raising interest within the RC pilot
community. The parkflier branch of Hobbico is coming out with
a 1.5 pound EDF jet capable of 90+mph right out of the box.
This is an incredible feature on its own, but Flyzone didn't
stop there: they made it scale, and nicely so. The airplane
is a scale model of the L-39 Albatross - In fact, Flyzone likes
the look of their latest release so much that they even include
a stand to go with it.

The real L39 is an east European sub-sonic jet aircraft, and
although it has been lightly armed, its main purpose is for
training. It was introduced in the late 60s, and has been a
commercial success. It is used both for military application
and in the civil world. The Breitling
precision jet team, among others, uses the L-39 for
their performance in aerobatic maneuvers.

The Flyzone L-39 comes in only one level of completion: Receiver
Ready (Rx-R). That means that the only things to add are the
receiver and the battery.

Product Details

Manufacturer's
description:

The high-viz trim scheme is already applied. A power system,
most onboard gear, and all hardware are ready to go, installed
at the factory. And the only assembly that remains is
easy and over with in about 15 minutes. Add a receiver
and a charged 4S pack and your departure time is minutes
after you get to the field. Give it a hand launch, and
it settles down into smooth, easy-handling flight almost
immediately. Blip the throttle and it's suddenly downfield
and disappearing fast. Line up for a low pass, push the
throttle to the firewall ? and feel the rush that
you've been waiting for.

Manufacturer:

Flyzone

Wingspan:

25
in (635 mm)

Length:

31
in (780 mm)

Wing
Area:

141
in² (9.1dm²)

Weight
Range:

24-25 oz (680-710 g)

Wing
Loading:

24.5-25.5
oz/ft² (75-78 g/dm²)

Battery

4S
2200mAh LiPo battery pack

Requires:

4-channel
radio
micro-receiver

Price:

$180
(as of time of review)

First
Look

Only
one version of the L-39 exists: the receiver ready Rx-R.
So only one box variant ? there is no mistake
possible when picking up the L-39 at the local hobby
shop.

The plane comes with a stand so you can have it as a
desk or shelf decoration when it is not screaming at
the local airfield. It is made of painted extruded polystyrene
(XPS). The jet?s name is cut on side, which add
to the cool factor.

Used
for the review

The
L-39 only requires a 4-channel receiver, and the smaller
size the better. However, the range cannot be compromised.
The model is fast and might quickly be out of range
if using an indoor/parkflier receiver. We selected the
R6106HFC for its mid-range capability while keeping
a compact size.

We
used the recommended battery: ElectriFly 4S 2200mAh
30C. The battery is 105mm x 34mm x 32mm (from measurement,
not including the wires) and fits just right in the
cockpit. The inside of the fuselage looks bigger than
it really is: the canopy takes some space, and the battery
has to be rightfully placed for the canopy to close
properly.

Assembly

Flyzone
did most of the work for us, and there is not much left to the
user to do. All the servos, linkage, ESC, motor, fan and other
accessories are already installed. The assembly consists in
gluing all the main elements together. Let's put it this way:
the overall building time is about equal to the time it takes
for the epoxy to cure.

A thin layer
of epoxy is spread on the wing saddle and the mating surface
of the wing. It is good practice to poke a few holes on both
of this surface. The epoxy doesn't bound very well on Aerocell,
but it is still mechanically strong. The epoxy will spread in
the holes and cavities before setting. The stabilizer and the
vertical fin are attached in the same manner to the fuselage.

Make sure to align
the stabilizer with the fuselage before the epoxy cures.

The
L-39 takes shape in no time. We are really within the
proper definition of an Almost Ready to Fly: the plane
is nearly complete out of the box, but still needs some
workshop time before heading to the field.

A
side note on the benefits of using tip tanks

The
tip tanks have very peculiar effects on airplanes,
which can be somewhat conter-intuitive. What could
be the benefit of adding this large tank to the
tip of the wing rather than slightly enlarging the
fuselage to have the extra-fuel imbedded in the
most flow-efficient way?

There
are many benefits in adding the tanks to the wing tips:

they
reduce the bending moment on the wings by deporting
a fraction of the mass to the wing tips. The overall
weight of the aircraft stays the same (or maybe slightly
increased), but it is better spread on the wing
spar.

Well
designed, they reduce the overall drag by acting
as a winglet and prevent the formation of the wing
tip swirl. This is specially true at low speed when
the induced drag increase is prevalent to the parasite
drag. A plane design for high speed is better off
without using tip tanks, as exemplified by "Pipsqueak",
an L-39 modified for racing with no tip tank.

On
some airframe, they can be retrofitted later. Many
companies offer tip tank upgrade kits for commercial
airplanes to increase their autonomy.

Designing
tip tanks is a balancing exercise between several parameters,
among which drag plays an important role. They do have
many pros, but not all planes will benefit from storing
fuel at their wing tips.

While
the L39 was designed with tip tanks Pipsqueal, the
L39 modified for racing, had her tip tanks replaced
by winglet to optimize the airflow at high speed.

Flight Report

There
is always some apprehension on a first flight of a hand-launched
racer. If the low speed capability is not there, it will be
a battle until the aircraft gain some velocity. If, on top
of that, something is not setup properly, the flight might
take a wrong turn.

So, here we are at the airfield with the newly built L-39
ready for take-off. A helpful hand is requested for this first
launch. The Flyzone video shows that is perfectly doable for
the pilot to launch the plane himself, but for now, I'd rather
have both hands on the remote, just in case. The helper grabs
the L-39 by the fuselage, from the top. Full throttle is applied,
and small rotation of the shoulder later, the plane is airborne.
It goes straight and out, and that is reassuring. The next
few passes are used for trimming the plane, and the jet needs
more than a few clicks to fly level and straight, but once
set, it goes right on trajectory.

The photograph already requests low passes for the camera,
so the L-39 is brought a series of lazy-8 a few meters above
the runway to get shot from every angles.

The first impression is positive: the L39 is well-behaved
at low speed, landing should be a breeze. The jet tends to
oscillate a bit on the roll axis, but nothing severe. Despite
not having a rudder, it remains perfectly controllable and
docile.

Alright, enough pictures, times to release the Watts! At full
throttle, the trajectories are ballistic, and the tiny jet
is very quickly out of the comfortable line of sight. No blinking
allowed!

The plane
literally screams at maximum speed. The motor-fan unit is
working hard at transforming the flow of electrons into airspeed.
Some may want to have a quieter power unit, but that would
come at a cost of efficiency. As a general rule, a fan efficiency
increases with rotational speed and diameter. Well, the diameter
is fixed by the size of the plane, so the designer had to
work on something, and that something now screams through
the sky, for the pleasure of my ears, and (probably) the discomfort
of all animals around the runway.

When it came to land, the jet was brought above the grass
for a nice gliding finale on the short grass. This little
screamer is easier to land that most trail draggers.

This
first very good experience with the L-39 was followed
by many others. As mentioned earlier, the plane can fly
relatively slow, but it is really at full throttle that
it thrives. The speed is exhilarating. The L-39 can do
all aerobatic maneuver in the book. Well, as long as the
rudder is not needed, that is. With the power on hand,
the only limit to the diameter of a loop is the eyesight
of the pilot. The roll rate is fast and it is better to
fly on low rate for long and clean trajectories.

Not everything was beautiful and pretty during the course
of the review. The hand launch is real easy with a true
and tuned model, but if something goes wrong, it goes
really wrong. The plane was obviously designed for performance,
not strength. The L-39 is unlikely to survive an unplanned
encounter with planet Earth. It is a good thing
that Towerhobbies is selling every pieces of the airframe
as spare parts!

So
if you are building your new L-39, be careful and double
check a few things. Here are a few problems that we had
to deal with:

A servo linkage for one aileron came off in flight.
The little black snap-ring on the back of the linkage
connection was lost in flight. The L-39 responses
became very sluggish, yet controllable. We could land
with no damage.

The elevator servo developed some play in its pocket
after several flights. That caused the trim to be
completely off on one of the take-off. The L-39 went
straight down, and the pilot had just enough throw
to redress and skim the underneath of the plane on
the runway and fly off. The canopy popped, and the
battery moved. The rest of the flight would be best
described as frantic.

Conclusion

With
the L39, Flyzone aimed at satisfying the speed addicted
among us and they hit the target just right. The jet is
a terrific bullet to fly. It is very enjoyable to look
at, both on a ground and in flight, which add even more
to the overall pleasure. The plane comes with an efficient
and powerful power plant and is correctly priced.

The L39 is designed for high performance and it shows
when the plane is airborne. Overall, the plane is well-engineered,
and the only place that would beneficiate from some improvement
is the front of the fuselage, where the battery could
be better secured, and the stabilizer servo less exposed
and more firmly attached.

Don't be fooled by the foam airframe, the flyzone L39
is a performance aircraft, which will bring joy to its
pilot when properly maintained.

Some additional data - we tested the L-39 with the Hobbico Big 5 GPS Logger, and the results are:
- speed passes measured from 90 to 96mph
- altitude: approx.850 ft before it was really too small to be seen.

The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.